Method and apparatus for bending wood



Aug. 23, 1932. F. c. BRANDENBURG METHOD AND APPARATUS FOR BENDING WOOD 2 Sheets-Sheet Original Filed Sept. l, 1927 I VH ttoz wat,

Aug. 23, 1932. F. c. BRANDENBURG I v 1,873,276

- METHOD AND APPARATUS FOR BENDING woon Original Filed Sept. l. 1927 2 Sheets-Sheet 2 attorney* Patented Aug. 23, 1932 nutren STATES FRANCIS c. BRANDENBURG, OFIJIQUA, OHIO, AssIGNOHTO .THE 4woon sHovHLANn* TOOL COMPANY, or Premi; OHIO, cenrona'rIoN or OHIO r l 'f METHOD AND ArraiiAfrUs nonBE'NDINeWOOn Application inea september 1,1927, serial No1 216,9.12Lv` anevyeaaanuary 13,1932,

This invention relates to bending wood; e. g., wooden handles for shovels. A very large proportion of shovel handles require a reverse-curve bend at the end which Igf, att-achesto the blade of the shovel, and a constantly increasing number of these handles require an additional bending Operation at the other end, whereby a fork is formed to e receivea handle grip.V VFor many years the most satisfactory method known for bending these handles has been that ofV boiling or steaming them and then pushing them endwise' into forms having the curvature it was desired to impart to the handles, and leaving them in the forms until the wood dried. To

permit removal of the handles from them,'the forms have consisted of planar channels having the required lateral curvature, and the handles were removed at the open side ofthe 2l) channels. These forms were made of cast or malleable'iron. A serious objection to this method lay in the large percentageV of loss through the handles breaking, or `the wood being so badly cracked orjsplintered as to make the handles useless, or at least reduce them to the grade of seconds Another difculty. has been the staining of many of the handles through some chemical action between the wetwoodv and metal forms.. Bemoval of this stain was expensive, and 1t was not always possible to remove it.

After long experimentation, and trial of different kinds of forms, I found that by using a substantially tubular form a large reduction in the percentage of loss through breakage, cracking and splinteringV was effected. But I found the discoloration of the wood increased, due to the fact that drying of A the wood was retarded by its more nearly forms easily and noiselessly, while'considefr Y able groaning and chattering accompanies their entranceinto untinned forms.v Possibly this chattering has ya disintegrative'eifect on the wood, and that its elimination reducesthe loss I have referred to. g

Ifsha'll now proceed todescribe the Ypreferred embodiment 'of my invention, and its operation, with the drawings,in which, s

Fig. lshowsa what isknown as the split D type.V 'It is to be aid ofthepac'companying .l

bent-wood' shovel vhandlefof understood lthat in practice the fork" at the left hand end of'thisfigure does not lie in-the same planeas the bend in the right hand end, butit lies 'ein a plane perpendicular to4 the right hand end so that when the'handle is put on a shovel the fork will lie'in a plane parallel to the shovel blade;

being bent to the form shown in Fig l; I l

Fig.` 3 illustrates the `form for'bending the right handend of the handle sho-wn in Fig.` l

f Figal illustrates the form for bending` the this View the machine isequipped with-the i form shown in Fig. preparatory to bending the right hand end of thehandle'shownfin Figl; 'Figc 6 is a plan of the Ijig for supporting the formfshown in Fig. 3, showing the forni inplace; A

Fig. 7 is an elevation of the jig shown in Fig. 6; and

Fig. 8 is a plan o f a portion of the machine 'Y shown in Fig. 5.v

The form for bending the'low'er endof the handle, the end shown at the rightha'nd in Fig. 1, is Well illustratedin Fig. 3,'and come prises members 25 and 26, so connected at27 by'a hinge that the members lcan be separated,

as is indicated with dotted lines'. Each of these members is semi-annular in cross section, sowhen the membersare together, as in Fig. 3, they form substantially atube.y One end of this tube is obstructed* the hinge,

but the other end is'open. The'handles 4are Fig.'2 shows the handle as it appears before I.

bent, after having been steamed or boiled to p make them pliable, by forcing them endwise into the tube through the open end. The members 25 and 26are held together with U shaped clamp, the ends of which are seen at 28-28 in Fig. 3. The clamp is left on'the form and the form on the handle until'the wood drieswhich requires about forty-eight hours. the members swung apartV` to release lthe handle. The longitudinal curvature Vof the members and 26, and therefore 'of the form as a. whole, is appropriately' similar toy thev curvaturewto be imparted to the handle. Thatis, the curvature' is enough different from that desired in the handle, so the handle ,will have thel desired curvature after it nspringsback a littleupon being released from the form.v f Y Referring now to Fig., 5, I shall describe the machine for bending these handles. `As this machine is'of a well known and. commonly used-type, it will suficeftorsay it comprises a .bed plate 30'mounted on suitable legs 31. Slidably mounted upon the bed is what 'l Ashall'call a pusher, forwant of a better name. lThis is indicated by the numeral 32, and at one end .the pusher carries a roller 33. Suitably journaled on the bedis a shaft 34,'which carries a cam adapted to bear on the roller 33 and move thepusher in one direction. The shaft is rotated through suitable speed-re ducing gearingby a belt, not shown, which runs on a pulley 36. Obviously, the shaft may be rotated by other means, if desired. The pusher is retracted by ta weight, not

. shown,ibutother means may be employed to do this.v Thebending form lies in a 1g, com- `pri'sing a plate 42 bolted to the bed 30 and avingi guide lugs 37, andan abutment38 which receives Ythe thrust as the handle-is pushed, into the form. See alsoy Figs. 6 and 7. Art'39y a recess is formed `in the plate 42 to accommodatebne legV ofthe clamp 28which holds Vthe form closed.. See also Fig. 3. Having laid a form in the jig, the operator holds the steamed end of the handle 41 in the mouth ofthe form, with the other endof the the shaft 34 drivenat such velocitythat after thepusher recedes, under the action ofthe weight before mentioned, the operator has time enough to yremove the handle, to put a Y new form in the jig and get a new handle into place by the time the cam begins to move the pusher forwardagain.

It will be observed that the member 25 of the form lies on one side, and the member 26 on the oppositeside of the neutral surface of the handle 4l. It follows that the mem- The clamp is then knocked off yand bers 25 and 26, whose circular cross section has about the same radius as that of the handle, invest the handle, giving support to its fibres during the time the fibres are subject by forcing it endwise into a sinuous channel .the walls, of whichare. parallel'to the neutral surface of the handle as the handle assumes the sinuous form imparted by the walls of the channel in other words, wherein the walls are tangent to the circular cross section of the handle. The contacts of thehandle withV the Walls of such a channel are mere lineson opposite sides of the axis of the handle', and

whateverbending moment is imparted to the 'i remaining parts ofthe handle canv only be suchasis transmittedy through that (what-V ever it is) which binds the bresof'thewood together. lt is because in the y,past handles have been bent in forms of thisikind that the loss through breakage has been so great. In my tubular or investing forms bending mo? eol i ment is applied directly to the major part of the handle surfaceand thus this severe strain on the integrating, elements of the woodv 1s eliminated. This has resulted in a large reduction in the breakage or splintering of the Wood. While the formanay be arranged to completely surround the ,handle l prefer to provide for a narrow space between the contiguousedges of the members 25 and 26, as

in Fig. 3. This servesr to ventilate the handle and facilitate its drying. On the. other hand,

the lack of complete investment or lenclosure of the handle is immaterial, since the open v space is near'the neutral surface, where the strain onthe wood is comparativelyslight.

While the forms may be madeof other materials I prefer to make them of. cast iron.

While cast iron stains the-handles, have found that by tinning the iron this difliculty is eliminated. The forms might be made entirely of tin, but to get sufficient strength they would need to be much thicker, and they wouldthe-n be heavy and clumsy ,to handle. Moreover, the cost-would-be prohibitive. lt

isr not necessary todescribe the method of ,g

tinning the iron as'the practice ofk coating iron with tin is very old and the manner of doing it is well imderstood` by many persons. It is quite common to tin articles made of cast or malleable iron, ywhere they may ybe subjected to Vconditions which would cause them to rust. For example, the metal parts oficecream freezers are commonly tinned;

- the left hand end of the handle shown in Fig.

l. At a glance it will be seen that Athis form is in effect two forms of the type shown in Fig. 3, enabling the two tinesto be. bent v simultaneously. This form contains a central member 50, of skeleton-like formation, having the general form of a wedge. That is, it has a thin end 51 and thick end 52, similar to a wedge. It differs from an ordinary wedge in that its sides have the reverse curvature which it is desired to impart to the tines off the fork. As is indicated by the sectional insert, in Fig. 4, the transverse lines of the wedge are straight, being made so because the transverse lines of the inner surn faces of the tines are straight. Referring to Fig. 2 it will be seen that the tines 53 are produced by making a saw cut 54 down the center of the turned Vstaff1 or handle 41. The annular groove 55 near the end'is merely a provision for securing the grip'to the tines and is not concerned with the present invention. Apposed to each side of the wedgelike member 50 is a form member 55, each of which is attached to the thick end of the wedge by a hinge 57 In cross section the members`56, at least their innerportions7 are semi-circular. In fact, these members are l substantially the same in cross section as the members 25 and 26.

Referring nowto Fig. 8, it will be seen that the bending machine is there fitted with a jig adapted to receive the tine-bending forms. This jig comprises a plate 60, upon which is a boss 61 having the contour of the central opening 62 in the wedge 50, shown in Fig. 4. The form is laid on the plate with the boss 61 in the opening 62 in the wedge and thus the form is anchored to the plate while the tines are pressed into the form. The plate 60 is bolted to the bed 30 of the machine in place of' the plate 42 previously described. This plate'is provided with a recess to receive a U shaped clamp 64, which clamp is set in the recess before the bending form is put in place, with the legs of the clamp pointed upward. The purpose of this clamp is to connect the free ends of the members 56 and hold them a `predetermined distance apart, while permitting the members to move laterally with reference to the thin edge of the wedge. The operator holds the slotted end of the handle 41 in the mouth of the form, with theslot parallel to the thin end of the wedge, until the block 40 on thepusher l32 impinges on the other end of the handle; The pusher then forces the handle into the form. The edge 51 ofthe wedge separates the tines 53-53, one tine entering the space between one member 56 and the wedge, the other tine entering the space between the other member 56 and the wedge. The form and handle are then lifted out of the machine as a unit and the form is left on the handle until the wood dries, after which the clamp 64 is knocked off and the form removed.

While it is intendedto cut the slot 54 in the center of the handle, the cutis sometimes slightly off-center. In such cases freedom of vthe members 56-56 to move laterally` as a unit with reference to the point of the wedge, permits automatic adjustment of the relative sizes of the spaces into which the tines are entering, appropriate to the unequal thickness of the tines'. This prevents excessive strain on either tine, with resulting elimination of breakage which might otherwise oocur.- This self-accommodation of the form also takes care of cases where the pliability ofthe tines is unequal' because of some inequality in the wood,its gra-in, ete".V -These forms are made of cast iron, and tinned for the same reasons as'I tin the forms 25-;-26,

and in both cases. the resulting reduction' in friction effects a vconsiderable reduction l'in loss from breakage of handles'. Friction is caused partly by adhesion of the p'arts'and partly by their roughness. As the chattering,

in untinned forms to the intermittent adhesion, sticking, of the wood Aandhiron, and as tinning the forms eliminates the chatter'-` ing, it is plain that there is much less adhesion between the wood'and tin thanbetween lthe wood and iron. Where both ends' of the handle are bent, asin Fig. 1, instead of using the block 40 and having it bear on 4the end three to twelve percent of the handles bent. Y

It isnot to be understood that my invention is limited in Vits scope to the particular embodiments shown,the scope ofthe invention. being limited only bymy claims, which areasfollowsf` Y 1.' A form for bending wood, comprising .two members having acurvature appropriately similar to the curvature to be imparted to the wood, said members being "situated `in apposition with a space between them sutil# cient to admit the piece of wood to be bent, the surfaces upon which the wood slides as it is pushed into the form being composed of metal between which andthe wood there is much less adhesion than there would, be between castiron and the wood.

2. A form for bending wood, comprising two members having, a curvature appropri- A. f'

ately similar to the curvature to be imparted to the wood, said members being situated in apposition with a space between them sufficient to admit the piece of wood to be bent,

the surfaces upon which the wood slides as d which I have previously described,is due $5 i Y it is pushed into the form beingcomposed of tin. n c Y v '3. 1A, formvfor bending wood, comprising a tube composed ofsections, and'm'eans enabling the' sections to be separated suiiiciently to remove the bent wood therefrom, the surfaces-'of the tube upon vwhich the wood slides as it is pushed thereinto being composed of metal between which and the Vwood there is much less adhesion than there would be be tween cast iron and the wood.

.14. A form for bending wood, comprising a tube composed of united sections, and means enabling the sections to be separated suihciently to remove the bent wooditherefrom,

the `surface upon which the wood slides as it isfpushed into' the form being composed of c metal between which andthe Wood there is much less adhesion than there Vwould be between cast iron and the wood and whichV will not stain the wood. f Y 5. A form for simultaneously bending both halves of a slotted wooden shaft to produce n the fork of a split D handle, said form *com*n prisingxa wedge, each. side whereof has the curvature which is'to be imparteduto the tines of the fork; a member on each side of said wedge having 'a curvature complemen- I tary to the aforesaid curvature of the adj a@ Y thin end of the wedge while'the tines'are being pushed into the form.

Y 6. A form for simultaneously bending both halves of a slotted wooden shaft to produce I ,the fork of a split D handle, said form com- 'prising a wedge, each side whereof has the curvature which is to be imparted to the tines of said fork; a member on each side of said wedge having a curvature complementary to if, that of the' adjacent wedge-side and spaced from said side a suificientvdistance to admit one of said tines, the ends of said members contiguous to thefbroad end of they wedge being maintained at the required distance therefrom by hinges which permit the members to swing outward for releasing the fork after it has become set to the form, 'and means connecting the free `ends of said members and keepingvthem a predetermined distance apart,` whileuleaving them free to move laterally as a unit with'V reference to the thin end of the wedge.

7. rA forni for simultaneously bending both halves of a slotted wooden shaft to produce the fork of a split D handle, said form coinprisiiig awedge, each side .whereof has the curvature` which is tobe imparted to the tines of the fork; a member ,on each side of said wedge having a curvature complementary to theAv aforesaid curvature of',v the adjacent wedge-side and spaced therefrom a sufficient distance to admit one tine ofthe fork, each vof said members combined with the contiguous wedge side forming a tube havinga cross- ,l

8. A form for simultaneously bendingvboth j halves of a slotted' wooden shaftjto produce the fork ofa split D handle, comprising two n passages, each having a curvature substantially such as is to be imparted to the tines of said fork, said passages 'being so disposed, relative to each other, that said halves .of the shaft can be pushedy endwise into said pas- I sages simultaneously, one halfentering each passage, said form being made of metal coatV- ed'with tin, whereby to make'movement of Y the wood in said passagescomparativelyfree from friction. f

9. kA form for simultaneously bending both t distance to admit one tine of the fork, and

means connecting said members and Vkeeping them a predetermined distance apart, which means permits the members vto move laterally as a unit with reference to the thin endjof the wedgeV while the tines are being pushed into the form, the surfaces on whichr` the wood slides as 'it is pushed into the'forni being composed of metal between which and the wood there is much less adhesion than there would be between cast iron and the wood'. 7

10. A formV for simultaneously bending both halves of -a slotted wooden shaft to p ro duce the fork of a split D handle, said form comprising a wedge, each side whereof has the curvature which is to be imparted to the 4 tiiies of the fork; a niemberon each side of said wedge having a curvature complementary to the aforesaid curvature of the adjacent wedge-side and spaced therefrom a sufficient distance to admit one tine ofthe fork, and means connecting said members and keeping them a predetermined distance apart, which means permits the members to move laterally as a unit with reference to the thin end ofthe wedge while the tines arey being pushed into the form, the Vsurfaces on which the wood slides as it is pushed into the form being composed of tin. v Y

1l. A form for simultaneously bending both halves of a slotted shaft to'produce 'the fork of a splitl D handle, comprising two,

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passages, each having a curvature substantially such as is to be imparted to the tines of the fork, said passages being so disposed, relative to each other, that said halves of the shaft can be pushed into the passages simultaneously, onehalf entering each passage, the surfaces of said form upon which the Wood bears as it slides tl ereinto being made of metal between which and the Wood there is very little adhesion.

12. The method of bending Wood, which comprises pressing the Wood endvvise into a form .having substantially the curvature to be imparted to the Wood7 Which form invests the Wood, thereby imparting bending moment directly to the parts of the Wood Which otherwise Woulc. undergo severe disV integrative strain, making the portions of the form on Which the Wood slidesof tin.

13. The method of bending Wood Which comprises pressing the Wood cndwise into a 'form having substantially the curvature to be imparted to the Wood, which form invests the Wood, thereby imparting bending moment directly to the parts of the Wood which other- Wise would undergo severe disintegrative strains, making the portions of the form on Which the Wood slides of a metal that o'ers very low resistance to the sliding of the Wood.

14. The method of bending Wood Which comprises pressing the Wood endvvise into a form having substantially the curvature to be imparted to the Wood, making the portions of the form on Which the Wood slides of a metal that oilers very lovv resistance to the sliding of the Wood.

FRANCIS C. BRANDENBURG. 

